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Stabilizing perovskite solar cells requires consideration of all defective sites in the devices. Substantial efforts have been devoted to interfaces, while stabilization of grain boundaries received less attention. Here, we report on a molecule tributyl(methyl)phosphonium iodide (TPI), which can convert perovskite into a wide bandgap one-dimensional (1D) perovskite that is mechanically robust and water insoluble. Mixing TPI with perovskite precursor results in a wrapping of perovskite grains with both grain surfaces and grain boundaries converted into several nanometer-thick 1D perovskites during the grain formation process as observed by direct mapping. The grain wrapping passivates the grain boundaries, enhances their resistance to moisture, and reduces the iodine released during light soaking. The perovskite films with wrapped grains are more stable under heat and light. The best device with wrapped grains maintained 92.2% of its highest efficiency after light soaking under 1-sun illumination for 1900 hours at 55°C open-circuit condition.

We report on the acquisition and modeling of the transient response of a commercial silicon (Si) solar cell using a benchtop pulsed X-ray source. The solar-cell transient output to the X-ray pulses was acquired under the dark and steady-state light illumination to mimic the practical operation of a solar cell under different light illumination levels. A solar-cell circuit model was created to develop a fundamental understanding of the transient current/voltage response of solar cell at read-out circuit level. The model was validated by a good agreement between the simulation and experimental results. It was found that the solar-cell resistance ( $R$ ) and capacitance ( $C$ ) depend on the light illumination, and the resulting variation in $RC$ time constant significantly affects the solar-cell transient response. Thus, the solar cell produced different transient signals under different illumination intensities in response to the same X-ray pulse. The experimental data acquired in this work proves the feasibility of using solar panels for prompt detection of nuclear detonations, which also builds a practical mode of X-ray detection using a low-cost self-powered detector.

The instability of metal halide perovskites (MHPs) remains to be one major obstacle for the commercialization of perovskite solar cells. Here we report the observation of nanocrystals and some amorphous phases at the surface of apparent single crystalline grains in polycrystalline films deposited by almost all known solution deposition methods, which accelerate the degradation of MHPs. By removing the defective surface layer through mechanical polishing, the stability of perovskite films is significantly enhanced. Encapsulated solar cells based on polished MHPs retain 93% of their initial efficiency after continuous illumination for 2180 hours at 1 sun intensity and with ultraviolet radiation at 65 °C. Removing the defective surface layers restores the mechanical hardness to be comparable to that of single crystals, which suppresses ion migration and permeation of detrimental species into perovskite grains. This study narrows down the stability gap between the MHP polycrystalline films and single crystal perovskites which represents the upper limit for the stability of MHPs.

Summary The presence of a defective layer composed of nanocrystals and amorphous regions at the surface of perovskite films has been shown to initialize the degradation of perovskites and cause nonradiative recombination. Here, we report the discovery that these defective surface layers are mechanically softer than the crystalline regions. The defective surface layer has a weaker bonding with the crystalline layer underneath it, which enables a facile approach to mechanically peel-off these defective layers using adhesive tapes. The chosen low-cost tape has an appropriate bonding force with perovskites, so the peeling does not damage the crystalline region and embedded interfaces underneath. The tape-treated devices retained 97.1% of the initial efficiency after operation at the near maximum power point under one sun illumination for 1,440 h at 65°C. This method is universally effective in enhancing the stability of various commonly used perovskite compositions and is compatible with the scaling up of perovskite solar modules.

Grain boundaries have been established to impact charge transport, recombination and thus the power conversion efficiency of metal halide perovskite thin film solar cells. As a special category of grain boundaries, ferroelastic twin boundaries have been recently discovered to exist in both CH3NH3PbI3 thin films and single crystals. However, their impact on the carrier transport and recombination in perovskites remains unexplored. Here, using the scanning photocurrent microscopy, we find that twin boundaries have negligible influence on the carrier transport across them. Photoluminescence (PL) imaging and the spatial-resolved PL intensity and lifetime scanning confirm the electronically benign nature of the twin boundaries, in striking contrast to regular grain boundaries which block the carrier transport and behave as the non-radiative recombination centers. Finally, the twin-boundary areas are found still easier to degrade than grain interior., Grain boundaries are known to be generally detrimental to the operation of metal halide perovskite solar cells. Here Xiao et al. show with scanning photocurrent microscopy that ferroelastic twin boundaries are benign to the electrical properties in crystalline samples, in contrast to grain boundaries.

Summary Integrating perovskites onto textured silicon provides a pathway to 30% tandem solar cells. However, deposition of 0.5–1 μm thick perovskite layers from solution onto textured silicon with typical pyramid heights of 3–10 μm remains a challenge. We propose a new tandem architecture that enables scalable, solution-based blading of perovskites onto silicon wafers textured with pyramids less than 1 μm in height. These pyramids are rough enough to scatter light within the silicon nearly as efficiently as large pyramids but smooth enough to solution-process a perovskite film. A nitrogen-assisted blading process deposits both a conformal hole transport layer and a planarizing perovskite layer that fully covers the textured silicon, at a speed of 1.5 m/min. With a textured light-scattering layer added to the top of the tandem to reduce front-surface reflectance, we achieve a perovskite/silicon tandem cell with an efficiency of 26% on textured silicon.

Mapping perovskite trap states The high efficiency of hybrid inorganic-organic perovskite solar cells is mainly limited by defects that trap the charge carriers and lead to unproductive recombination. Ni et al. used drive-level capacitance profiling to map the spatial and energetic distribution of trap states in both polycrystalline and single-crystal perovskite solar cells. The interface trap densities were up to five orders of magnitude higher than the bulk trap densities. Deep traps were mainly located at the interface of perovskites and hole-transport layers, where processing created a high density of nanocrystals. These results should aid efforts aimed at avoiding trap-state formation or passivating such defects. Science , this issue p. 1352

Perovskite solar cells (PSCs) are promising to reduce the cost of photovoltaic system due to their low-cost raw materials and high-throughput solution process; however, fabrication of all the active layers in perovskite modules using a scalable solution process has not yet been demonstrated. Herein, the fabrication of highly efficient PSCs and modules in ambient conditions is reported, with all layers bladed except the metal electrode, by blading a 36 ± 9 nm-thick electron-transport layer (ETL) on perovskite films with a roughness of ≈80 nm. A combination of additives in phenyl-C

Perovskite light-emitting diodes (PeLEDs) are promising candidates for display and solid-state lighting, due to their tunable colors, high conversion efficiencies, and low cost. However, the performance of blue PeLEDs is far inferior to that of the near-infrared, red, and green counterparts. Here, the fabrication of pure-blue PeLEDs with an emission peak at 475 nm, a peak external quantum efficiency of 10.1%, and a maximum luminance of 14 000 cd m-2 is demonstrated by tailoring the compositions of perovskites. The pure-blue electroluminescence is achieved by simultaneous addition of rubidium and chlorine ions into CsPbBr3 and incorporation of phenylethylammonium chloride forms quasi-2D hybrid perovskites. The combination of these composition engineering results in blueshifted emissions without reducing the quantum yield. The judicious alloying is shown to be critical to result in the better morphology with suppressed current leakage and enhanced light outcoupling.

The interfaces of perovskite solar cells (PSCs) are important in determining their efficiency and stability, but the morphology and stability of imbedded perovskite-substrate interfaces have received less attention than have top interfaces. We found that dimethyl sulfoxide (DMSO), which is a liquid additive broadly applied to enhance perovskite film morphology, was trapped during film formation and led to voids at perovskite-substrate interfaces that accelerated the film degradation under illumination. Partial replacement of DMSO with solid-state carbohydrazide reduces interfacial voids. A maximum stabilized power conversion efficiency (PCE) of 23.6% was realized for blade-coated p-type/intrinsic/n-type (p-i-n) structure PSCs with no efficiency loss after 550-hour operational stability tests at 60°C. The perovskite mini-modules showed certified PCEs of 19.3 and 19.2%, with aperture areas of 18.1 and 50.0 square centimeters, respectively.

In this study, we evaluated the feasibility of applying solar photovoltaic (PV) panels as sensors of nuclear and electromagnetic radiation that includes neutrons, x-rays and gamma-rays, and optical radiation emanating from a nuclear explosion. We investigated the steady-state and transient response of both a commercial silicon (Si) and a perovskite solar cell to different radiation types. Solar cell current-voltage characteristics and short-circuit current (I sc ) response under steady-state x-ray illumination were measured. The fast transient radiation pulse from a nuclear detonation was mimicked by using a fast switching, nanosecond pulsed laser source and the transient response of the solar cells was captured on an oscilloscope. Subsequently, the transient response of Si solar cells to pulsed x-rays generated by a mechanical x-ray chopper was measured. A 2 MeV neutron beam chopper was built at the fast neutron beam facility of a research reactor to produce time-modulated neutrons and evaluate the solar cell transient response to a neutron pulse. Our steady-state measurements demonstrated good response of solar cells to x-rays and neutrons. The pulsed radiation measurements indicated that the solar cells are able to detect a fast transient radiation and produce a proportional measurable output signature.

It is well recognized that the thickness of TiO2 film serving as hole blocking layer (bl-TiO2) in planar n-i-p structured perovskite solar cells is required to be thin for the purpose of reducing c...

Paper-based electronics have obtained increasing attention as they offer benefits of light weight, flexibility and low cost. In this work, heat-resistant borosilicate glass paper, showing extraordinary flexibility and being able to be treated at high temperature (~500 °C), is used as the substrate for flexible dye-sensitized solar cells (DSSCs) for the first time. High-quality photoanodes were prepared via a novel sequent filling method with the aid of poly(methyl methacrylate) PMMA and ice layers, leading to smooth and continuous TiO2 film. A complete different device structure design compared to the conventional one was also brought about, by taking advantage of using this photoanode as solid-state electrolyte supporter and being further connected with the counter-electrode. The prototype solar cell was successfully demonstrated for the first time, with a decent initiating photovoltaic performance, resulting in an efficiency of 0.85% (open-circuit voltage, Voc=0.67 V; short-circuit current density, Jsc=...

NiOx is a promising hole-transporting material for perovskite solar cells due to its high hole mobility, good stability, and easy processability. In this work, we employed a simple solution-processed NiOx film as the hole-transporting layer in perovskite solar cells. When the thickness of the perovskite layer increased from 270 to 380 nm, the light absorption and photogenerated carrier density were enhanced and the transporting distance of electron and hole would also increase at the same time, resulting in a large charge transfer resistance and a long hole-extracted process in the device, characterized by the UV–vis, photoluminescence, and electrochemical impedance spectroscopy spectra. Combining both of these factors, an optimal thickness of 334.2 nm was prepared with the perovskite precursor concentration of 1.35 M. Moreover, the optimal device fabrication conditions were further achieved by optimizing the thickness of NiOx hole-transporting layer and PCBM electron selective layer. As a result, the bes...

An alternative ink design is introduced that enables fast coating of perovskite at room temperature for low-cost solar modules., The efficiencies of small-pixel perovskite photovoltaics have increased to above 24%, while most reported fabrication methods cannot be transferred to scalable manufacturing process. Here, we report a method of fast blading large-area perovskite films at an unprecedented speed of 99 mm/s under ambient conditions by tailoring solvent coordination capability. Combing volatile noncoordinating solvents to Pb2+ and low-volatile, coordinating solvents achieves both fast drying and large perovskite grains at room temperature. The reproducible fabrication yields a certified module efficiency of 16.4%, with an aperture area of 63.7 cm2. This method can be applied for various perovskite compositions. The perovskite modules also show a small temperature coefficient of −0.13%/°C and nearly fully recoverable efficiency after 58 cycles of shading, much better than commercial silicon and thin-film solar modules.

Anchoring monolayer bilateral amines on perovskite passivates surface defects, reinforces grain boundaries, and enhances stability., The power conversion efficiencies (PCEs) of perovskite solar cells (PSCs) are already higher than that of other thin film technologies, but laboratory cell-fabrication methods are not scalable. Here, we report an additive strategy to enhance the efficiency and stability of PSCs made by scalable blading. Blade-coated PSCs incorporating bilateral alkylamine (BAA) additives achieve PCEs of 21.5 (aperture, 0.08 cm2) and 20.0% (aperture, 1.1 cm2), with a record-small open-circuit voltage deficit of 0.35 V under AM1.5G illumination. The stabilized PCE reaches 22.6% under 0.3 sun. Anchoring monolayer bilateral amino groups passivates the defects at the perovskite surface and enhances perovskite stability by exposing the linking hydrophobic alkyl chain. Grain boundaries are reinforced by BAA and are more resistant to mechanical bending and electron beam damage. BAA improves the device shelf lifetime to >1000 hours and operation stability to >500 hours under light, with 90% of the initial efficiency retained.

Although the two-step deposition (TSD) method is widely adopted for the high performance perovskite solar cells (PSCs), the CH3NH3PbI3 perovskite crystal growth mechanism during the TSD process and the photo-generated charge recombination dynamics in the mesoporous-TiO2 (mp-TiO2)/CH3NH3PbI3/hole transporting material (HTM) system remains unexploited. Herein, we modified the concentration of PbI2 (C(PbI2)) solution to control the perovskite crystal properties, and observed an abnormal CH3NH3PbI3 grain growth phenomenon atop mesoporous TiO2 film. To illustrate this abnormal grain growth mechanism, we propose that a grain ripening process is taking place during the transformation from PbI2 to CH3NH3PbI3, and discuss the PbI2 nuclei morphology, perovskite grain growing stage, as well as Pb:I atomic ratio difference among CH3NH3PbI3 grains with different morphology. These C(PbI2)-dependent perovskite morphologies resulted in varied charge carrier transfer properties throughout the mp-TiO2/CH3NH3PbI3/HTM hybrid, as illustrated by photoluminescence measurement. Furthermore, the effect of CH3NH3PbI3 morphology on light absorption and interfacial properties is investigated and correlated with the photovoltaic performance of PSCs.

NiO

With power conversion efficiencies now reaching 24.2%, the major factor limiting efficient electricity generation using perovskite solar cells (PSCs) is their long-term stability. In particular, PSCs have demonstrated rapid degradation under illumination, the driving mechanism of which is yet to be understood. It is shown that elevated device temperature coupled with excess charge carriers due to constant illumination is the dominant force in the rapid degradation of encapsulated perovskite solar cells under illumination. Cooling the device to 20 °C and operating at the maximum power point improves the stability of CH3 NH3 PbI3 solar cells over 100× compared to operation under open circuit conditions at 60 °C. Light-induced strain originating from photothermal-induced expansion is also observed in CH3 NH3 PbI3 , which excludes other light-induced-strain mechanisms. However, strain and electric field do not appear to play any role in the initial rapid degradation of CH3 NH3 PbI3 solar cells under illumination. It is revealed that the formation of additional recombination centers in PSCs facilitated by elevated temperature and excess charge carriers ultimately results in rapid light-induced degradation. Guidance on the best methods for measuring the stability of PSCs is also given.

Perovskite solar cells have shown remarkable progress in recent years as power conversion efficiencies have already eclipsed 24%—highest of all thin film photovoltaic technologies. In addition to unprecedented optoelectronic properties unseen in traditional semiconductors, low formation energy and solution processability open the door to low-cost and high throughput solution coating strategies for commercialization. This review presents recent work on the fabrication of perovskite films by meniscus coating—a simple and readily scalable manufacturing technique—which includes blade coating and slot die coating. The article outlines the fundamental fluid mechanisms of meniscus coating, discusses drying and crystallization of the perovskite during the coating process, and provides an overview of progress in meniscus-coated perovskite solar cells and modules.

A novel amorphous cobalt potassium phosphate hydrate compound (KCoPO 4 ·H 2 O) is identified to be active photocatalyst for oxygen evolution reaction (OER) to facilitate hydrogen generation from water photolysis. It has been synthesized through a facile and cost-effective solution-based precipitation method using earth-abundant materials. Its highly porous structure and large surface areas are found to be responsible for the excellent electrochemical performance featuring a low OER onset at ∼550 mV SCE and high current density in alkaline condition. Unlike traditional cobalt-based spinel oxides (Co 3 O 4 , NiCo 2 O 4 ) and phosphate (Co–Pi, Co(PO 3 ) 2 ) electrocatalysts, with proper energy band alignment for light-assisted water oxidation, cobalt potassium phosphate hydrate also exhibits robust visible-light response, generating a photocurrent density of ∼200 μA cm −2 at 0.7 V SCE . This catalyst could thus be considered as a promising candidate to perform photoelectrochemical water splitting.

We report herein perovskite solar cells using solution-processed silver nanowires (AgNWs) as transparent top electrode with markedly enhanced device performance, as well as stability by evaporating an ultrathin transparent Au (UTA) layer beneath the spin-coated AgNWs forming a composite transparent metallic electrode. The interlayer serves as a physical separation sandwiched in between the perovskite/hole transporting material (HTM) active layer and the halide-reactive AgNWs top-electrode to prevent undesired electrode degradation and simultaneously functions to significantly promote ohmic contact. The as-fabricated semitransparent PSCs feature a Voc of 0.96 V, a Jsc of 20.47 mA cm(-2), with an overall PCE of over 11% when measured with front illumination and a Voc of 0.92 V, a Jsc of 14.29 mA cm(-2), and an overall PCE of 7.53% with back illumination, corresponding to approximately 70% of the value under normal illumination conditions. The devices also demonstrate exceptional fabrication repeatability and air stability.